Siemens SIMATIC NET PROFIBUS, Owner'S Manual

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Infrared Link Modul (ILM)
6ZB530–3AC30–0BA1
14 Copyright
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by Siemens
A further application of a point-to-point link is described below. Figure 4 shows how several slave network
segments can be connected to one master network segment using their own infrared transmission links.
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Once again, make sure that the infrared transmission links do not interfere with each other, in
other words either the spatial arrangement of the modules (clearance) or a physical barrier (wall)
must ensure that each PROFIBUS ILM can only detect the emission of its partner module and
cannot detect emissions from the modules of the other infrared links.
If this is not guaranteed, this can lead to problems in the master network segment. The response of a slave
node is detected at slightly different times in the master segment due to the unsynchronized operation of the
PROFIBUS ILM causing pulses to be lost on the master network segment.
The advantage of this arrangement is that if there is a problem on an infrared link between two PROFIBUS
ILMs, only the connected slave segment is disconnected. The master network segment and the other slave
network segments retain their functionality. This topology is also suitable when the PROFIBUS ILMs of the
slave network segments cannot be arranged so that they are all located in the light cone of the PROFIBUS ILM
on the master network segment.